Late last year, Nas announced that his new album would be called Nigger, prompting howls of protest from Al Sharpton, Jesse Jackson and the NAACP — a formidable phalanx of opponents, even for one of rap’s most hardened battlers. Nas eventually backed down, and the CD now bears no title. But the cover art — an arresting image of the rapper’s bare back, lashed with whip marks that form the letter “N” — leaves little doubt about the album’s real name.

Still, the music is the farthest thing from shallow provocation. For 15 years, Nas has been the standard-bearer for New York rap traditionalism: a prodigiously skilled lyricist with an old-fashioned commitment to street reportage and a lust for scorched-earth rhyme battle. His main theme has been his inner struggle — torn between the allure of gangstadom and his loftier impulses — but on Untitled, Nas turns his gaze outward. This is a sprawling, furious, deeply ambivalent theme album about institutional racism, the failures of black leadership and the pathologies and promise of early-21st-century African-American life. It is also the closest hip-hop has come to a semiotics seminar — an album-length meditation on the meanings, ambiguities and historical ironies of the n word. In short, it is the most intensely political record since the heyday of Public Enemy and Ice Cube, with Nas sounding as virtuosic as he did on his 1994 debut, Illmatic.

At the center of it all is that incendiary six-letter epithet. In “Y’all My Ni**as,” he raps, “We changed the basis of derogatory phrases. . . . Now people are mad if they ain’t one.” In “Untitled,” Nas champions the word as an honorific for all revolutionaries: “Be the resistance/No matter what color you are/Everybody niggas.” Throughout, he plays the politically incorrect trickster, resisting easy sloganeering, denouncing Bill O’Reilly on the one hand and hip-hop materialism on the other, gleefully exploiting racist and misogynist minstrel-show stereotypes in songs like “Fried Chicken” and “Project Roach.”

Nas has often taken a perverse approach to record production, confessing to interviewers that he avoids memorable hooks because they would distract from his lyrics. Untitled includes tracks from A-listers Cool and Dre, Stargate and Mark Ronson, but the neosoul-flavored sounds and unadorned beats are almost militantly dull. Sometimes, the beats aren’t beats at all: “Queens Get the Money” finds Nas freestyling over wan piano filigree, with nary a drum or bass to be heard.

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Luckily, the rhymes reward close listening. “N.I.*.*.E.R. (The Slave and the Master)” is an epic packed with vivid details: “I come from the ghetto/Where old black women talk about they sugar level.” But Nas is also a fierce battle-rhymer, reeling off punch lines — “I’m over they heads, like a bulimic on a seesaw” — and tight couplets: “You ain’t as hot as I is/All of these false prophets is not messiahs/You don’t know how high the sky is/The square mileage of Earth, or what pi is.”

This talk of messiahs is nothing new. Nas titled his 2002 album God’s Son and has often styled himself as rap’s savior and martyr. On 2006’s Hip Hop Is Dead, he concluded that the genre would perish unless resurrected by . . . Nas. And on Untitled‘s booming lead single, “Hero” (produced by Polow Da Don), he accuses his record company of something close to crucifixion: “This Universal apartheid/I’m hogtied, the corporate side.” Nas’ self-righteousness can make his records heavy going. The sanctimony even seems to seep into his flow; his lyrics are often brilliant, but his rapping is unmusical, lacking the joyful swing of his fellow first-tier MCs.

Still, on Untitled, Nas has found subject matter worthy of his grandiosity and his grumpiness. And the album holds a surprise: a song about a savior who isn’t Nas. Untitled ends with “Black President,” an ode to the man Nas calls a “new, improved JFK”: Barack Obama. Fittingly, on a record full of conflicted feelings and complicated politics, the rapper’s endorsement is wary and measured: “I’m thinking I can trust this brother.”